Medium for use in preparing transparent prints



Patented Jan. 8, 1946 FOR USE IN PREPARING TRANSPARENT PRINTS Louis S. Sanders, Shaker Heights, Ohio No Drawing. Application September 17, 1943,

- Serial No. 502,796

3 Claims.

This invention relates, as indicated. to a medium for use in preparing transparent prints and to a method of making such medium.

It has heretofore been common practice in preparing tracings from which blu prints and other prints are prepared to first make a pencil drawing on tracing paper, and then, since such drawings are usually so smudged up by the hands as to render them unsuitable for making blue prints therefrom, to transfer such drawing to a final tracing, executed in waterproof or India ink, such final tracings being then used to make blue prints or the like.

In certain types of work, as for example, in making third-dimensional or perspective drawings, such final tracing has manually applied thereto shading, which may take the form of stipplln parallel lines, crossed lines, and the like. Aside from the fact that the preparation of tracings in this manner is slow and laborious and is highly undesirable, particularly at the present time, when there is such a shortage of skilled draftsmen and artists, the application of the shading by hand defeats the very purpose of preparing a final tracing, since the tracings are likely to become smudged up .by the artists in applying the shading.

The present invention has as its primary ob- Ject the preparation of a medium which may be used in preparing a substitute for a so-called "final" tracing, and the use of which will obviate the necessity of executing an ink drawing such as has been described.

Another object of the invention is to provide a medium which may be used in preparing such a substituta and which may have shading applied thereto in a rapid and easy manner and without the danger of smudging or otherwise damaging the same.

A further object of the invention is to provide a medium which may be used in preparing a substitute for a final tracing, and from which blue prints and other contact prints of high quality may be quickly and easily prepared.

A still f rther object of the invention is to provide a novel method of preparing such a medium.

Other objects and advantages of the invention will be apparent during the course of the following description.

In preparing the medium of the present invention, I first take a sheet of a transparent material, such as is commonly used for making tracings, i. e., tracing paper or tracing cloth, and then apply to one surface of said sheet a chemically-developable pattern which may consist of a multiplicity of closely spaced tiny dots, lines,

stipples or any other similar pattern suitable for backgrounding or shading an image or point producedonsaid sheet.

This pattern may be produced photographically, as described in Baker Patent No. 1,709,600,

or may, be imprinted on the paper as described in Maier et al. Patent No. 1,778,397 or McIntosh Reissue Patent No. 20,503, but I prefer to apply the pattern on the sheet in the manner described in McIntosh Patent No. 2,301,900, in which case the pattern will be not only photographically invisible, but transparent as well.

After the pattern has been thus applied to one surface of the transparent sheet, I apply to the sheet, preferably to the surface opposite that to which the pattern has been applied, a coating of a suitable light-sensitive emulsion, such for example as is commonly used for coating Van Dyke, blue print or Ozalid print paper, such emulsions containing in general complex silver compounds and/or iron salts. The application of such emulsion renders the sheet opaque or translucent.

The sheet of paper thus coated forms the medium of the present invention, and may be used in the following manner.

A pencil drawing, such as an ordinary mechanical drawing, is first prepared on a sheet of tracing paper, as hereinbefore described, but instead of transferring such drawing to a final tracing by hand, I bring such drawing into contact with the emulsion-coated surface of a sheet of the medium of the present invention and expose the drawing to light, as'in making ordinary contact orblue prints. In this way, I form a print of the drawing directly on the medium of my invention and subsequently develop the contact print thus formed, either by the usual wet methods or by means of a gas as in making Ozalid prints. I prefer dry methods of developing the print, since such methods are less likely to aifect the photographically invisible and transparent pattern on the reverse side of the sheet.

The portions of the light sensitive (emulsion which have not been affected by the exposure to light are removed from the sheet, as by washing or rinsing the sheet in clean water, or by the dry method used in the Ozalicl process, leaving a transparent sheet bearing the opaque lines of the print on one surface thereof and the chemically-developable pattern on the other surface thereof.

After the sheet has been dried, selected portions or areas of the pattern may be rendered \visible to form" a background or shading for the For this purpose suitable developing agents such as.

Print on the other surface of the sheet.

asolution of caustic soda may be-used as. in the aforesaid Bake-r :patent or a solution containin hypo and sulphide or a solution of a sulphide as a1. patent. Due to the fact that the sheet is transparent, the'development of the pattern at the desired places is rendered easy. Moreover, since the development of the pattern is'accomplished on the reverse side of the sheet from that hearing the print of the drawing, such print is less likely to be smudged or otherwise damaged than if the print were on the same surface. of the sheet as that bearing the pattern. It is to be understood, however, that I do not intend to limit the invention to a method wherein the emulsion is applied to the reverse side of the sheet from that bearing the pattern, but the emulsion may, if desired, be applied to the same surface as that bearing suchpattern.

described in the aforesaid Maier et.

The print or "final" tracing, as thus prepared,

is eminently suited for makingcontact prints, or,

engineering copies, since all of the sharpness of detail of the original pencil drawing as well as the developed pattern, is preserved in the print. Since the original drawing is not transferred to my medium by hand, the time necessary for the execution of the transfer is eliminated, and the resulting print or drawing is free from dirt or smudge marks which would. otherwise be transferred to the drawing.

I' am aware that in my Patent No. 2,146,653

I have described the preparation of a medium for ing: transparent prints or tracings, as is my present transparent sheet. Moreover, the sheet in the aforesaid patent bears the light-sensitive emulsion on thev same surface of the sheet which bearsthe chemically developable pattern, whereas, in the preferred form of the present invention, the light-sensitive emulsion is onl the reverse side of the sheet, with the result that development of the pattern as shading is less likely to smudge or otherwise damage the print.

It is to be understood that the form of my invention, herein described, is to be taken as a preferred example ofthe same, and that various changes may be resorted to without departing from the spirit ofv my invention, or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. A medium for use in preparing transparent prints suitable for making contact prints, which comprises a transparent sheet having on one surface thereof a c'hemicallydevelopable photographically invisible pattern, and a coating of a light sensitive material on the other surface of said: sheet, the pattern bearing. portion of the one. surface overlying at least'in part the coatnag bearing portion of. the other surface of said s act.-

2. A medium for use in preparing transparent prints suitable for making contact prints, which comprises a transparent basesheet having on one surface thereof a chemically-developable photographically invisible pattern, and a coating of a light sensitive material on the other surface of said'sheet.

3. Amedium for use inpreparing transparent prints'to be used in making contact prints, whichcomprises a transparent base sheet having thereon an: overall chemicall'y-developable photographically invisible pattern andan overall'coating of a light sensitive material on the opposite surface of the base sheet.

LGUIS S. SANDERS. 

